At large work sites such as rock quarries and mines, an unmanned vehicle travelling system is introduced to operate unmanned dump trucks instead of manned vehicles such as manned off-road dump trucks in order to improve productivity by avoiding an accident due to workers' fatigue, manpower saving, and extension of working hours at the time of sediment transportation work.
The work site where the unmanned dump trucks travel includes respective areas such as a loading place, an earth removal place and the like. Each area is connected by a maintained carrying path which is called a whole road and by an intersection or a lead-in path, which is called an access road, extended from the whole road to each area.
The work sites have a plurality of unmanned dump trucks, and the respective unmanned dump trucks travel to their destinations along travel routes which are independently generated depending on respective purposes. But, the respective travel routes might interfere with other travel routes at an intersection or an alternate one-way traffic section. If an unmanned dump truck stops in a region interfering with another travel route, the operation of the respective unmanned dump trucks might fall in deadlock. In this specification, the situation “the vehicle operation falls in a deadlock state” is called “deadlock”.
According to a conventional technology, the travelling system that causes a plurality of vehicles to travel did not consider a problem of deadlock at all or was limited to a special case only even if the problem was considered.
In Patent Document 1, the travel route is divided into respective segments, a position of an unmanned vehicle is reported to a monitoring device every time the unmanned vehicle passes through each segment, and the monitoring device which has received the position report checks that there is no interference and gives the unmanned vehicle approval to travel through the next segment. If the unmanned vehicle cannot receive travel permission, the unmanned vehicle is automatically stopped. And, if unmanned vehicles are located adjacent to each other, communications are mutually made between them to check that the travel routes are not interfered with each other.
In Patent Document 2, unmanned vehicles are alternately caused to travel through the alternate one-way traffic section, so that the unmanned vehicles are prevented from interfering with each other.
Patent Document 3 relates to a traffic control system for manned vehicles, and when a traffic signal at the intersection in front of a vehicle changes its color, it is automatically judged whether the vehicle should pass through the intersection or should stop before the intersection, thereby preventing interference at the intersection.
Patent Document 4 that causes unmanned forklifts to travel along indoor travel routes, and generates travel routes including a turning route where the unmanned forklifts are turned such that they do not interfere with facilities such as indoor walls and the like.
Patent Document 5 prevents interference between an unmanned dump truck and a loader by prohibiting the unmanned dump truck from entering into a loading area having the loader therein.    Patent Document 1: Japanese Patent Application Laid-Open No. H10-222227    Patent Document 2: Japanese Patent Application Laid-Open No. 2001-109519    Patent Document 3: Japanese Patent Application Laid-Open No. 2002-170198    Patent Document 4: Japanese Patent Application Laid-Open No. H2-96809    Patent Document 5: Japanese Patent Application Laid-Open No. H9-198134
Patent Document 1 merely divides into segments and does not consider deadlock in an interference region such as an alternate one-way traffic section or an intersection, so that there is a possibility that deadlock occurs in the alternate one-way traffic section or the intersection to immobilize unmanned vehicles.
Patent Document 2 can prevent interference between unmanned vehicles in the alternate one-way traffic section only, but since it does not consider interference in another intersection or a more complex interference region, deadlock might be caused in such an interference region.
Patent Document 3 is a system assuming a manned vehicle and cannot be applied to an unmanned vehicle traveling system that originally does not estimate visual recognition of a signal. And, interference can be prevented at an intersection where traffic signals are provided, but deadlock might be caused in such an interference region because interference in an alternate one-way traffic section or a complex interference region is not considered.
Patent Document 4 can prevent one unmanned forklift from interfering with an indoor facility, but since interference among a plurality of vehicles outdoors is not considered at all, it cannot be applied to an unmanned vehicle travel system by which a plurality of unmanned vehicles are caused to travel outdoors.
Patent Document 5 can prevent interference between an unmanned dump truck and a loader in a loading area, but deadlock which might be caused between the unmanned dump trucks in an interference region such as an alternate one-way traffic section or an intersection is not considered at all. Therefore, there is a possibility that deadlock occurs in the alternate one-way traffic section or the intersection, and the unmanned dump trucks are immobilized.